Temperature-indicator.



C. LE 6. FORTESCUE.

TEMPERATURE INDICATOR.

APPLICATION FILED FEB. 21. 1911.

1,156,680. Patented Oct. 12, 1915.

ATTDRNEY M Wan/W UNITED STATES PATENT OFFICE.

CHARLES LE G. FORTESCUE, ,OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WEST-INGHOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OFPENNSYLVANIA.

TEMPERATURE-INDICATOR.

Application filed February 21, 1911.

To all whom it may concern:

Be it known that I, CHARLES LE G. Fonrusccn, a subject of the King ofGreat Britain, and a resident of Pittsburgh, 1n the county of Alleghenyand State of Pennsylvania, have invented a new and useful Improvement inTemperature-Indicators, of which the following is a specification.

My invention relates to temperature indicators for electrical apparatuswhich is immersed in or otherwise influenced by a cooling medium, and ithas special reference to transformers which are employed in connectionwith electric railway systems on which the overloads are frequentlysudden and excessive.

The object of my invention is to provide a device of the aboveindicated'class which shall be simple and inexpensive in construction,reliable and sensitive in operation and particularly adapted to registerthe temperature of the copper in the transformer coils.

In thepast it has been customary to equip transformers of relativelylarge capac1ty with thermometers which projected into the tanks and wereimmersed in the insulating oil contained therein. Thus, the thermometerregistered the temperature of the 011 which, in case of normal andstable operation, was an approximate indication of the temperature andcondition of the transformer coils. It is evident that such a de vicegave only approximate indications of the existin conditions, on accountof the large body of oil to be heated and the high specific heat thereofand, hence, was considered useful only in installations where the loadwas steady or subject to only gradual and comparatively narrowfluctuations.

With the use of transformers in the feeder systems of electric railwaysand railroad electrifications on which the demand fluctuated within widelimits, and excessive overloads of comparatively short duration werefrequent, the indications of such thermometers were unreliable anduseless. For instance, although a serious and damaging overload mightoccur upon the transformer, the total heat generated in the copperduring .the period of overload would not be'sufiicient toraise thetemperature of the oil to a point that would materially affect thethermometer, and hence, the indications would be of no value.

It is the purpose of my present invention Specification of LettersPatent.

Patented Oct. 12, 1915.

Serial No. 609,941.

to overcome this difiiculty and provide means whereby the therl'nometerwill register accurately-and quickly the temperature of the copper inthe transformer coils. I accomplish this result by reproducing theconditions which affect the temperature of the coil copper, and I securethese conditions by influencing the thermometer by the insulating oiland also in proportion to the current which traverses the transformerwindings. In order to produce the required degree of sensitiveness andaccuracy, very careful and precise experimental adjustments arenecessary, as will be hereinafter set forth. It should be understoodthat my invention is not restricted to use with transformers but iscapable of application to any electrical apparatus which is affected byany cooling medium.

Figure 1 of the accompanying drawing is a view, partially in elevationand partially in vertical section, of a transformer which embodies myinvention, a portion of the apparatus being shown diagrammatically forsimplicity, and Fig. 2 is a view of a lranodified portion of the deviceshown in Referring to the drawing, the device here shown comprises acontaining tank 1, a thermometer 2, a transformer 3, a body ofinsulating oil 4, an auxiliary series transformer 5 and a heating coil6. The thermometer 2, which may be of any ordinary type of construction,is mounted on the containing tank 1 and is provided with a laterallyextending portion 7 which projects through a bushing 8 in the side ofthe tank 1 and is enveloped by a sheath 9 of good heat-conductingmaterial, the latter being immersed in the body of insulating liquid 4,in the usual manner.

The transformer 3 may be of any well known construction and comprises aplurality of transformer coils 10 which are assembled side by side upona suitable laminated core structure '11 which is firmly held together bymeans of upper and lower end frames12 and 13 and tie rods 14. Each ofthe transformer coils 10 is separated from adjacent insulating barriers15 by means of wave shaped spacing strips 16 which are disposedlongitudinally at the respective sides of said coils in order to providepassages 17 through which the insulating oil4 may circulate.

The auxiliary series transformer 5 forms no part of my invention, exceptas it performs a necessary function in its operation, and it may be ofany suitable construction. The primary winding 18 of the seriestransformer 5 is connected in series with the transformer coils 10,while its secondary winding 19 is connected to the heating coil 6 whichsurrounds a portion of the projecting member 7 of the thermometer 2. Alagging 20 of heat-insulating material envelops the heating coil 6, inorder to confine the heat of said coil and effectively impart it to thethermometer.

When the transformer is put into operation, the insulating oil 4,whichlies adjacent to the transformer coils 10 becomes heated and,consequently, rises to the top of the tank, whereby a circulation of oilis established through the passages 17 as will be readily understood.This circulation brings the heated oil into contact with the exposedsheath 9 and thus it cooperates with the heating coil 6 to influence thethermometer 2.

Those skilled in the art will understand that the actual temperature ofthe transformer coil copper depends upon the temperature of the oil inthe immediate neighborhood thereof, the amount of heat. dissipatedthrough the insulation of the coil and the current which traverses thetransformer coil. By means of the apparatus hereinbefore described, andcareful experimental adjustments which will be hereinafter set forth, Iproportionately reproduce the heating conditions which affect the copperof the transformer coils and apply the same to the thermometer 2,whereby the temperature of the copper is accurately indicated.

Having assembled the apparatus, as hereinbefore indicated, preliminaryadjustments are made experimentally to determine the correct amount ofheat to impart to the thermometer 2 through the agency of the heatingcoil 6, and subsequently to determine the proper physical and electricalproperties of the coil in order that the thermometer will besufficiently sensitive to changes in the temperature of the copper inthe transformer coils. These adjustments are accomplished as follows:Normal current is first allowed to flow in the transformer a sufficienttime to establish stable heat conditions of both the transformer coils10 and the insulating oil 4, after which the ratio of the seriestransformer 5 is varied until the heat generated in the heating coil 6is just sufficient to cause the thermometer 2 to register the correcttemperature of the transformer copper, as calculated in the usualmanner.

Although it will probably be preferable to accomplish this result byadjustments of the series transformer, which may conveniently beprovided with a plurality of taps (not shown) for the purpose, it willbe understood that any of the various other well known means for varyingthe heating effect of the coil 6 may be employed.

Having once arrived at the proper amount of heat for the coil 6 toimpart to the thermometer 2, it is merely a matter of adapting the coilso that the action of the thermometer will be sensitive and quick enoughto be of practical use. This is accomplished by subjecting thetransformer 3 to a slight overload and comparing the thermometerindication to the actual temperature of the coil copper as calculatedfrom the rise in resistance.

If it is found that the thermometer registers too low,it is evident thatthe heating coil 6 acts too slowly and must be adjusted to follow theactual temperature changes quickly. This may be done by keeping the heatgenerated in the coil 6 constant and equal to the amount previouslyexperimentally determined, maintaining the heating surface exposed tothe thermometer the same, and decreasing the amount of material in thecoil to be heated, thereby necessitating an increase in the currentdensity. Such an adjustment will tend to make the heat developed in thecoil 6 more effective in influencing the thermometer quickly and willtend to bring the temperature curve of the thermometer 2 co-incidentwith that of the copper in the transformer coils, which is essential ifthe indications of the thermometer are to correspond accurately to thetemperatui'of the coil copper, as will be readily understood.

It is not considered necessary to' describe in detail the specificadjustments just referred to, as it is merely a matter of design andexperiment, and it is believed that no difficulty will be experienced bythose skilled in the art in understanding the same.

If, after the foregoing adjustments have been made, it is found that thethermometer still lags in its action, careful and successive changesshould be effected in a manner similar to those hereinbefore set forth,until the thermometer finally becomes sensitive enough to accuratelyindicate the temperature of the copper in the transformer coils.

It may be found impossible to secure the desired degree of sensitivenessin this manner, which merely indicates that the rate of heat dissipationfrom the thermometer to the surrounding oil is insufficient. In thiscase, the coil 6 should be rewound to cover a reduced amount of thethermometer surface, after which a new preliminary determination of thecorrect amount of heat to generate in the coil is necessary. Thehereinbefore mentioned adjustments of the coil for the purpose of makingthe thermometer quickly responsive to variations in the temperature ofthe coil copper should then be efl'ected in the manner described, untilthe required degree of sensitiveness is obtained.

Under certain conditions, it may be desirable to change the design ofthe thermome ter itself by varying the size of the bulb, etc., in orderto accomplish the desired results.

It follows, of course, that converse adjustments of the heating coil 6should be made if the action of the thermometer is found to be inadvance of the actual transformer copper temperature.

In some cases. it may be preferable to dispose the heating coil 6 withinthe protecting sheath 9 and in intimate contact with the thermometer 2as shown in Fig. 2. Thus, the heat of the coil 6 is more effectivelyimparted to the thermometer.

\Vith single phase transformers having a plurality of independentsecondary coils and with polyphase transformers which are likely tocarry unbalanced loads, it will probably be expedient to provide eachwinding of the transformer with a temperature indicating device in themanner hereinbefore set forth.

Although I have shown and described a device of specific constructionand arrangement and location of parts, it is evident that variousmodifications may be effected without departing from the spirit andscope of my invention, and I desire that only such limitationsshall beimposed as are indicated in the appended claims.

I claim as my invention:

1. The combination with electrical apparatus enveloped in a coolingmedium, and a temperature-indicating device associated therewith andadapted to be influenced by said cooling medium, of stationary means forinfluencing said device in accordance with the current traversing saidelectrical apparatus.

2. The combination with an electric conductor, a cooling mediumenveloping the same, and a thermometer for indicating the temperature ofsaid conductor and adapted to be influenced by said cooling medium, ofelectro-thermal means associated with said thermometer for influencingsaid thermometer in proportion to the current traversing said electricalconductor.

3. The combination with an electric conductor, a cooling mediumenveloping the same, and a thermometer for indicating the temperature ofsaid conductor and adapted to be influenced by said cooling medium, ofelectro-thermal means associated with said thermometer for influencingsaid thermometer in proportion to the current traversing said electricalconductor, the relative influences being proportioned in accordance withpredetermined conditions.

4. The method of indicating the temperature of electrical apparatusWhich is envelature of an electric current conductor, which is thermallyassociated with a surrounding medium that consists in exposing atemperature indicator to the direct influence of said medium and inexposing said indicator to an additional influence which is dependentupon the current traversing the conductor, said influences beingproportioned to effect similar thermal characteristics in said conductorand said temperature indicator.

7 The combination with an electric current conductor surroundedby acooling medium, and a temperature indicator exposed to the influence ofsaid medium, of a heating coil associated with said indicator anddependent upon the current traversing said conductor for its influenceupon said temperature indicator.

8. The combination with an electric current conductor surrounded by acooling medium, and a temperature indicator exposed to the influence ofsaid medium, of aheating coil disposed around a portion of saidindicator and dependent upon the current traversing said conductor forits influence upon said indicator.

9. The combination with a liquid-containing tank, a transformer immersedtherein, and a thermometer, of electro-thermal means associated withsaid thermometer for causing said thermometer to indicate thetemperature of the copper in the transformer coils.

10. The combination with a liquid-containing tank, an electric deviceimmersed therein, and a thermometer projecting into said liquid, ofelectro-thermal means associated with said thermometer and with saidelectrical device for influencing the action of said thermometer.

11. The combination with a liquid-containing tank, a transformerimmersed therein, and a thermometer associated therewith and projectinginto said liquid, of electrothermal means for influencing saidthermometer in proportion to the current traversing the transformedcoils.

12. The combination with a liquid-containing tanK, a transformerimmersed therein. and a thermometer projecting into said liquid, ofelectro-thermal means dependent upon the current flowing in saidtransformer for causing said thermometer to indicate the temperature ofthe copper in the transformer coils.

13. The combination with a transformer immersed in an insulating liquid,and a thermometer adapted to be influenced in accord ance with thetemperature of the insulating liquid. of means electrically associatedwith said transformer for influencing said thermometcr in proportion tothe current in said transformer.

11. The combination with a main transformer, an insulating medium. and atemperatlire-indicating device adapted to he influenced by saidinsulatin means, of a series transformer having; its primary windingconnected in series with said main transformer, and a heating coilassociated with said temperature-indicating device and connected to thesecondary winding of said series transformer.

15. The combination with a liquid-containing tank. an electric deviceimmersed therein. a temperature-responsive device projecting into thesaid liquid. of electrothermal means associated with the said temperature-responsive device and with the said electrical device forinfluencing the action of the said temperature-responsive device.

In testimony whereof. I have hereunto subscribed my name this 13th dayof Feb. 1911.

CHARLES LE G. FORTESCUE.

Witnesses W. M. McCoxAisEv, B. B. Hixizs.

